It doesn't go away anytime soon. At my companies association we had the lawn crew come in and dump 100 yds of mulch in the parking lot. Moron didn't use a tarp, we still have a stain going on 2 months and it's not looking like it will disappear anytime soon. He also let marks all over with his skid steer. Rookie company, bad owner, crappy employees. I would tell the customer that the option to use a non died mulch is always there, but if he doesn't want to go that route he will have some staining if any mulch is left outside of the bed.